22,289 research outputs found

### The $\omega NN$ couplings derived from QCD sum rules

The light cone QCD sum rules are derived for $\omega NN$ vector and tensor
couplings simultaneously. The vacuum gluon field contribution is taken into
account. Our results are $g_\omega =(18\pm 8), \kappa_\omega=(0.8\pm 0.4)$.Comment: To appear in Phys. Rev. C (Brief Report

### $\pi \Delta\Delta$ coupling constant

We calculate the $\pi \Delta\Delta$ coupling
$g_{\pi^0\Delta^{++}\Delta^{++}}$ using light cone QCD sum rule. Our result is
$g_{\pi^0\Delta^{++}\Delta^{++}}=(11.8\pm 2.0)$.Comment: RevTex, 5 pages + 1 PS figur

### Y(4143) is probably a molecular partner of Y(3930)

After discussing the various possible interpretations of the Y(4143) signal
observed by the CDF collaboration in the $J/\psi \phi$ mode, we tend to
conclude that Y(4143) is probably a $D_s^\ast {\bar D}_s^\ast$ molecular state
with $J^{PC}=0^{++}$ or $2^{++}$ while Y(3930) is its $D^\ast {\bar D}^\ast$
molecular partner as predicted in our previous work (arXiv:0808.0073). Both the
hidden-charm and open charm two-body decays occur through the rescattering of
the vector components within the molecular states while the three- and
four-body open charm decay modes are forbidden kinematically. Hence their
widths are narrow naturally. CDF, Babar and Belle collaborations may have
discovered heavy molecular states already. We urge experimentalists to measure
their quantum numbers and explore their radiative decay modes in the future.Comment: 6 pages, 1 table, 4 figure

### Spin-1 charmonium-like states in QCD sum rule

We study the possible spin-1 charmonium-like states by using QCD sum rule
approach. We calculate the two-point correlation functions for all the local
form tetraquark interpolating currents with $J^{PC}=1^{--}, 1^{-+}, 1^{++}$ and
$1^{+-}$ and extract the masses of the tetraquark charmonium-like states. The
mass of the $1^{--}$ $qc\bar q\bar c$ state is $4.6\sim4.7$ GeV, which implies
a possible tetraquark interpretation for Y(4660) meson. The masses for both the
$1^{++}$ $qc\bar q\bar c$ and $sc\bar s\bar c$ states are $4.0\sim 4.2$ GeV,
which is slightly above the mass of X(3872). For the $1^{-+}$ and $1^{+-}$
$qc\bar q\bar c$ states, the extracted masses are $4.5\sim4.7$ GeV and $4.0\sim
4.2$ GeV respectively.Comment: 7 pages, 2 figures. arXiv admin note: substantial text overlap with
arXiv:1010.339

### Isospin breaking, coupled-channel effects, and X(3872)

We re-investigate the possibility of X(3872) as a $D\bar{D}^*$ molecule with
$J^{PC}=1^{++}$ within the framework of both the one-pion-exchange (OPE) model
and the one-boson-exchange (OBE) model. After careful treatment of the S-D wave
mixing, the mass difference between the neutral and charged $D(D^*)$ mesons and
the coupling of the $D(D^*)$ pair to $D^*\bar{D}^*$, a loosely bound molecular
state X(3872) emerges quite naturally with large isospin violation in its
flavor wave function. For example, the isovector component is 26.24% if the
binding energy is 0.30 MeV, where the isospin breaking effect is amplified by
the tiny binding energy. After taking into account the phase space difference
and assuming the $3\pi$ and $2\pi$ come from a virtual omega and rho meson
respectively, we obtain the ratio of these two hidden-charm decay modes:
$\mathcal{B}(X(3872)\rightarrow \pi^+\pi^-\pi^0
J/\psi)/\mathcal{B}(X(3872)\rightarrow \pi^+\pi^- J/\psi)=0.42$ for the binding
energy being 0.3 MeV, which is consistent with the experimental value.Comment: published in Phys. Rev.

### Possible $J^{PC} = 0^{--}$ Charmonium-like State

We study the possible charmonium-like states with $J^{PC}=0^{--}, 0^{-+}$
using the tetraquark interpolating currents with the QCD sum rules approach.
The extracted masses are around 4.5 GeV for the $0^{--}$ charmonium-like states
and 4.6 GeV for the $0^{-+}$ charmonium-like states while their
bottomonium-like analogues lie around 10.6 GeV. We also discuss the possible
decay, production and the experiment search of the $0^{--}$ charmonium-like
state.Comment: 12 pages, 10 figures, 3 table

### The electromagnetic decays of the charmed and bottom baryons in chiral perturbation theory

We have investigated the electromagnetic decays of the antitriplet and sextet
charmed baryon systems with $J^P= \frac{1}{2}^+, \frac{3}{2}^+$ in the
framework of the heavy baryon chiral perturbation theory. We first construct
the chiral Lagrangians at $O(p^2)$ and $O(p^3)$. Then we calculate the
electromagnetic (EM) decay amplitudes of the charmed baryon systems up to
$O(p^3)$. With the help of the quark model, we estimate the low energy
constants. The numerical results of the EM decay widths show good convergence
of the chiral expansion. We notice that the two neutral EM decay processes
$\Xi_c'^0\rightarrow\gamma+\Xi_c^0$ and ${\Xi_c^*}'^0\rightarrow\gamma+\Xi_c^0$
are strongly suppressed by the SU(3) U-spin flavor symmetry. With the same
formalism, we also estimate the EM decay widths of the bottomed baryons. The EM
decay widths of the heavy baryons may be measured at facilities such as LHCb
and JPARC. The explicit chiral structures of the heavy baryon decay amplitudes
derived in this work may be useful to the possible chiral extrapolations of the
future lattice simulations of these EM decay amplitudes

### Pentaquarks

Since LEPS collaboration reported the first evidence of $\Theta^+$ pentaquark
in early 2003, eleven other experimental groups have confirmed this exotic
state while many other groups didn't see any signal. If this state is further
established by future high statistical experiments, its discovery shall be one
of the most important events in hadron physics for the past three decades. This
exotic baryon with such a low mass and so narrow a width imposes a big
challenge to hadron theorists. Up to now, there have appeared more than two
hundred theoretical papers trying to interpret this charming state. I will
review some important theoretical developments on pentaquarks based on my
biased personal views.Comment: Review Commissioned by International Journal of Modern Physics

- â€¦